Electrical connector



NOV 7, 1939. G D E 2,178,621

' ELECTRICAL CONNECTOR Filed Feb. 1, 1937 Patented Nov. 7, 1939 ELECTRICAL CONNECTOR Gustaf E. Andre, Richmond, Ind, assignor to Belden Manufacturing 00., Chicago, 111., a

M corporation of Illinois Application February 1, 1937, Serial No. 123,335

3 Claims. (01. 1737-322) My invention relates to electrical connectors and has particular reference to detachable plug connectors of the type used for connecting electrical conductor cords to electrical appliances 6 such as toasters, fiat irons, and the like.

Connectors of this type usually comprise a hollow, elongated body member of insulating material having a plurality, usually two, socket type contacts supported in suitable open ended rem cesses formed therein. The individual conductors of the conductor cord with which the connector is used are attached to these contacts within the connector body member by suitable screws or the like.

, 3&3 During the use of conductor cords fitted with connectors of this type, it is very common practice for the user to effect the disengagement of the connector from the cooperating contact pins or the like forming a part of the appliance with which the connector is used by jerking or pulling the conductor cord. In the connectors heretofore known to the art, the stresses resulting from this pulling or; jerking of the cord have been applied directly to the electrical connection be- 25 tween the cord conductors and the connector contacts with the result that injury to the plug or its connections or even to the user have occurred. Fiu'ther, repeated application of such stresses tend to Wear the cord insulation and creso ate a serious fire hazard. In fact, the potential dangers and hazards of these older types of connectors are so great that the Insurance Under-- writers have recently promulgated a rule which provides, in effect, that connectors ofthis type must be capable of sustaining a weight of fifty pounds applied between the contacts and the associated conductor cord for a period of five minutes without permitting separation of the cord conductors and the contacts, even whenthe conao, tact'screws have been backed off sufilciently to substantially disconnect the cord conductors and the contacts. Obviously only such connectors as include means for mechanically connecting the conductor cord with the connector body to relieve 45 the electrical connections of theconnector from strain during use of the connector can qualify under this rule.

The principal object of the present invention I is to provide an improved strain relief for use w in conjunction with connectors of this general type which shall inherently prevent the tensional stresses which may be impressed upon the con-' ductor cord during use from being transmitted to the electrical connection between the cord con- 65 ductors and the connector contacts. Other objects of the invention are to provide an improved strain relief which shall be relatively simpleand inexpensive to manufacture and which may be utilized in conjunction with existingtypes of connector structures with little or no modiflca- I tion thereof; to provide an improved strain relief which shallutilize no metallic parts whatsoever, thereby-minimizing insulation and fire hazards; and, generally, to provide an improved strain relief and connector embodying the same. 19

While the present invention is applicable to various types of connectors and connector plug structures, it finds particular application to connectors of the general type disclosed in Patent No. 1,898,589 which was issued on February 21, 1933, to George J. Meuer, and in the accompanying drawing I have disclosed the features of one form of my invention'as applied to a connetor plug of the type shown in this patent. Referring to the drawing 2d Figure l is a side elevational view, partially in section, of a connector embodying the features of the present invention;

Figure 2 is a front elevational view, partially in section, of the connector illustrated in Figs ure 1;

Figure 3 is a sectional view on the general line 3-3 of Figure 2;

Figure 4 is a sectional view on the general line 4-4 of Figure 2; 80

Figure 5 is a perspective view of a cord and contact assemblage in accordance with the present invention preparatory to the insertion of the same within the body of the connector;

Figure 6 is a perspective view of a wedge mem- 85 ber forming a part of the preferred structure of the present invention; and

Figure 7 is a fragmentary view showing the operation of my improved strain relief.

The body of the connector illustrated in the drawing comprises two cooperating, complementary half sections I which are adaptedto be securely held together when the connector is assembled by a pair of U-shaped springs 3 which engage and fit within suitable recesses 5 formed in the sides thereof. The opposed faces of the two cooperating half sections l are hollowed out so as to define in the assembled connector two elongated recesses l for receiving and positioning two socket type contacts 9 adapted to cooperate with contact pins or the like forming apart of the appliance with which the connector is used. These recesses 1 are so formed that the socket contacts 9 are securely held against movement relative to the plug body when the connector is assembled and are open at the lower end, as is illustrated in Figure '7.

The conductor cord II with which the connector is used is of the usual two conductor type and is admitted into the interior of the connector 7 body through a generally cylindrical cord receiving passageway II extending inwardly into the upper end thereof. -The inner end of the cord receiving passageway l3 connects with the two contact receiving recesses I through a pair of generally L-shaped branch passageways l5 each of which is adapted to receive the end portion of one of the two conductors l'l making up the cord conductor II.

To minimize bending and kinking of the conductor cord ll adjacent the connector body, the connector includes an axially flexible protector spring IS the lower coils of which engage an annular recess 2| formed in the cooperating half sections I making up the connector body. A ferrule 22 may be provided at the outer end of this protective spring for engaging the-cord proper.

During the assembling of connectors of this type, the sheath of the conductor cord is cut away for a short distance so as to permit separation of the two conductors l1, then the ends of the metallic portion of these conductors are bared and attached to the socket type contacts 9, as is shown in Figure 5. Heretofore it has been customary to thereupon assemble the two half sections of the body about these contacts, the branched ends of the cord occupying the passageways l5. When so assembled, any force applied to the cord l I will be transmitted directly to the electrical connection between the cord conductors and the socket contacts, which condition it is the principal purpose of the present invention to overcome. However, I havediscovered that if the two branched ends of the conductors are stiffened and enlarged as by a tape, cord, or thread reenforcement 23 so as to increase the cross sectional area of each branch of the cord sufllciently to substantially completely fill the transversely extending portion of the passageway l5 within which that branch is located, and if the area of the central cord-receiving passageway is restricted adjacent the inner end thereof so that the body of the connector tightly grips the cord at this point, stresses impressed upon the conductor cord will not be transmitted to the electrical connection between the cord conductors and the contacts. Or in other words, a strain relief consisting of a mechanical interconnection between the cord II and the connector body will be realized.

The reenforcing is preferably extended up about the adjacent end of the cord proper for a short distance as illustrated at 24, and the restriction ofthe central passageway 13 at this point is accomplished by annular projections formed integrally with the cooperating half sections making vup the body. To minimize the amount of the reenforcement of the end of the conductor cord proper, it is desirable that the annular projections 25 shall restrict the area of the cord-recelvlng passageway l3 to a value not 'materially greater than the cross sectional area of the cord ll whereby interposition of the wrapping 24 will permit the projections 25 to tightly grip the cord at this point.

The combined cross sectional area of the two branch passageways IS in the planes A- A is preferably somewhat greater than the cross sectional area of the restricted portion of the central passageway l3, and sufiicient thread or other reenforcement is wound about thebranched ends ofthe conductor cords at 23 to assure that each of the branched ends shall completely fill the passageway within which it is'located, as is illustrated in Figures 2 and 4. This means that when a tension stress is applied to the cord H any movement of that cord with respect to the connector body will be resisted both by the wedging action resulting from the increased cross sectional area of the branched portions of the conductor cord as compared with the cross sectional area of the restricted portion of the central cordreceiving passageway l3 and by the right angle relationship between the branched ends of the conductor cord and the cord proper, which relationship tends to be maintained as a result of the stiifenlng imparted to the branched ends of the cord by the reenforcement 23. If desired, the reenforcement 23 on the branched ends of the cord conductor l I may be impregnated with shellac, varnish, or other substances capable of increasing the stiffness thereof with beneficial results from the viewpoint of increasing the strain resistance of the assembled connector.

While the mere winding of the branched ends of the cord conductor I I so as to completely fill the transverse portions of the branch passageways I 5 within the plug body produces a connector capable of withstanding relatively large tension stress without permitting any of that stress to be impressed upon the electrical connections of the connector, I have found that very greatly increased resistance to such stresses may be accomplished through the utilization of a wedging member 21 located within the connector body at the point of juncture of the two branches,

of the cord ll. One suitable form of wedging member 21 is illustrated in Figure 6 and comprises an elongated, parallelepiped, preferably formed of horn fiber or similar insulating material. This wedglng member 21 is adapted to be positioned within a suitable recess 28 formed in the cooperating half sections I, and is normally retained in the position shown in Figures 2 and 4 by this recess. When a strong-pull is applied to the cord II, the wedge member 21 tends to be drawn up into the restricted portion of the central cord-receiving passageway l3, as indicated in Figure 7, and serves to produce a wedging action resisting relative movement of the cord I l and the connector body.

It is desirable that the axial length of the wedge member 21 shall be slightly less than the diameter of the restricted portionof the central cordreceiving passageway l3. This assures that the wedging member shall be free to enter the restricted portion of the central cord-receiving passageway and thereby produce the maximum wedging effect upon the application of stresses to the cord. The use of the wedging member 21 is particularly desirable in conjunction with connectors having body sections held together by springs, because even when strong springs are used, there will be slight yielding'thereof 'under stress. Actual tests indicate that connectors embodying strain reliefs of the type described in the foregoing, when used without the wedge member 28 will uniformly resist tensional stresses in the neighborhood of sixty pounds, whereas when the wedging member 28 is utilized the ultimate resistance of the connector to such stresses will be increased to about ninety pounds.

From the foregoing i...- ill be seen that I have disclosed the features of a new form of strain relief particularly adapted for use in conjunction with the connector plugs employed for detachably connecting appliance cords to toasters, flat irons, and similar devices. The strain relief of my invention, while exceedingly simple in form and capable of use in conjunction with most of the known connectors of this type, is capable of relieving the electrical connections of the connector from all strains which might otherwise be induced during the use thereof, and when the strain relief construction embodies the we ing member disclosed as the preferred form of the invention, remarkable resistance to such stresses will be obtained. It will be uderstood by those skilled in the art that the strain relief.

of the present invention is applicable to connectors which are not held together by springs as, for example, the connectors disclosed in my earlier Patent No. 1,954,859, which was issued on April 17,1934. Also,it will be apparent to those skilled in the art that various strain relief structures embodying the principles disclosed in the foregoing may be developed. Accordingly, it is my intention that the accompanying claims shall be accorded the broadest reasonable construction consistent with the state of the art.

I claim the following as my invention:

1. In apparatus of the class described, a conductor cord which is provided with at least two separate conductors, and a connector for use in conjunction therewith, including means defining a body, a plurality of contacts supported within said body, a centrally arranged cord-receiving passageway adapted to receive one end of said cord and having a cross sectional area at least slightly less than the cross sectional area of said cord, in order that said cord shall be tightly gripped by the walls of said passageway, and a plurality of branch passageways extending genance and to increase the cross sectional area of said conductors to substantially the same value as the cross sectional area of the branch passageways within which they-are located the combined cross sectional areas of the separate conductors being greater than the cross sectional "area of said central passageway, the bent portions sitioned within said chamber, one end of said member contacting said bent portions and the other end thereof being supported on said adjacent wall, said wedging member being movable into said central passageway between the sew rate conductors when tensional stress is applied to said cord.

2. In apparatus of the class described, a relatively flexible conductor cord which is provided with two separate conductors, and a connector for use in conjunction therewith, the individual conductors making up said conductor cord being branched at the terminal end of said cord, and each of said branches being reenforced and stiflened by an insulating means applied thereto preparatory to the assembling of said connector, said connector including an insulating body provided with a central passageway for receiving one endof said conductor cord and with a pair of oppositely arranged branch passageways extending generally transversely to said central passageway for receiving the branches of said cord, and a wedging member positioned within said insulating body with one end thereof positioned adjacent the point of juncture of said central pasa sageway and said branch passageways, said body being provided with a recess, the other end of said wedging member in one position engaging within said recess said wedging member being adapted to be drawn into said central passageway upon the application of tensional stress to said conductor cord.

3. In apparatus of the class described; a relatively flexible conductor cord which is provided with two separate conductors; and a connector for use in conjunction therewith, including means defining an insulating body, a pair of contacts positioned within recesses within said body, a centrally arranged cord-receiving passageway adapted to receive one end of the cord conductor with which said device is used and having a cross I sectional area substantially equal to the cross sectional area of said cord, and a pair of oppositely arranged branch passageways extending generally transversely to said cord-receiving passageway; the individual conductors making up said conductor cord being branched at the terminal end oi said cord and being adapted to occupy said branch passageways; each or the branches of said cord being reenforced and stiflened by an insulating wrapping applied thereto preparatory to the assembling of said connector to increase their bending resistance and to increase the cross sectional area thereof to such an extent that the combined cross sectional areas 0! the branches of said cord are greater than the cross sectional area of said central passageway; said. connector also including va wedging member seated within a third recess formed therein adjacent the juncture of said branch 3 passageways and said central passageway, said wedging member being adapted to be moved out of said third recess and into said central passageway between the branches of said cord when tensional stress is applied to said cord.

GUSTAF E. ANDRE. 

